1. Field of Invention
The present invention relates to lock mechanisms of umbrella and more particularly to such a lock mechanism mounted in a large umbrella (e.g., beach umbrella, golf umbrella, or the like) capable of quickly effecting a multi-sectional length adjustment of a telescopic shank in response to strong wind.
2. Description of Related Art
A conventional large umbrella (e.g., beach umbrella, golf umbrella, or the like) 1 is shown in FIGS. 1 and 2. The umbrella 1 comprises a shank 11, a plurality of spreaders 12, a lower sliding sleeve 13, an elongate actuation member 14, a handle 15, and a hub (not shown) at a top of the shank 11. A plurality of link bars are interconnected the spreaders 12 and the sleeve 13. The actuation member 14 comprises an upper flexible element 16 having a curved portion urged against an inner wall of the shank 11, a lower tab 17 disposed in a lower aperture 19 of the sleeve 13 in a locked state of the umbrella, and a bottom push button 18 adapted to push to cause the tab 17 to clear the aperture 19 for unlocking the umbrella. That is, a simple pressing of the push button 18 can automatically open the umbrella.
However, the flexible element 16 may suffer fatigue after a predetermined period time of use. And in turn, it may compromise the desired lock mechanism of the umbrella. Still however, the shank 11 is an elongate member and is not telescopic. Thus, a person, particularly a short person, may encounter great difficulties of operating the umbrella by holding the shank 11 when wind is heavy. Yet however, a telescopic shank 11 still cannot solve the problem since the engagement of a tab 17 and an aperture 19 of a sleeve 13 is relatively weak for a large umbrella (i.e., not reliable in use). A large curved member projected from an outer surface of a shank may solve the problem. However, its bulky size may adversely affect a normal operation of the umbrella.
U.S. Pat. No. 6,684,893 discloses a simplified controlling apparatus of an automatic umbrella. The '893 patent describes a spring-biased control loop and a projecting button. A first pressing of the button is adapted to move the control loop inward for opening the umbrella. A further pressing of the button will push a bullet-head to disengage with a shaft, thereby enabling a closing of the umbrella. However, the '893 patent is typically relatively complex in constructions, costly to manufacture, trouble-prone, unreliable in use, and cannot be mass produced easily.
Moreover, ribs cannot dispose in parallel relationship with the shank in a closed state of typical umbrella due to structure factor. Thus, rib tips may entangle with other objects when the umbrella and the objects are placed together. Hence, a need has arisen for an improved lock mechanism of a large umbrella capable of effecting a multi-sectional length adjustment of its telescopic shank.